This invention relates to electrical connections for extremely fine wires (wires in the range of AWG 32-50) of the type widely used for the windings of small electrical coils. The herein disclosed embodiment of the invention is specifically intended for connecting relatively coarse insulated wires (e.g. AWG 20 wires) to the extremely fine wires of a coil wound on a bobbin. However, the principles of the invention can be used under other circumstances where connections to extremely fine wires are required.
Electrical coils, such as induction coils, composed of extremely fine wires are widely used in many branches of the electrical industry and it is quite often a requirement that the coil windings be connected to relatively coarse insulated wires which extend to the coil. In the past, it has been common practice to achieve these electrical connections by providing solder terminals on the bobbin on which the coil is wound and soldering both the external wire and the coil wire to the solder post. More recently, connecting devices for coil wires have become available which have wire-receiving slots therein, the slots being dimensioned to receive the coil windings and the external wires, see, for example, U.S. Pat. No. 3,979,615. These wire-in-slot or "displation" connecting devices are now being widely used and are replacing soldered connections to a large extent for many types of windings. However, if the coil windings are of wires smaller than about AWG 28 or 30, it is often impractical to use a displation type of electrical connection. For example, a AWG 50 wire has a diameter of about 0.001 inches and a slot dimensioned to receive an AWG 50 wire would, of necessity, have a width of less than 0.001 inches. The manufacturer of terminal devices having wire-receiving slots therein of one thousandths of an inch or less is a practical impossibility, and the solder technique is, therefore, still being widely used for connections to coil wires in these extremely fine size ranges.
In accordance with the principles of the instant invention, a terminal post of firm insulating material is provided which may be integral with a coil bobbin and the fine wire of the coil winding is wrapped around an intermediate portion of this terminal post. The electrical connection is achieved by providing a generally U-shaped terminal and crimping the terminal onto the post with the web portion of the terminal bearing against the fine wire windings on the post. The web portion of the terminal is, moreover, a spring which normally extends arcuately inwardly between the sidewalls of the terminal so that when the terminal is crimped onto the post, the arcuate web is partially straightened. As a result, the web is compressively stressed along its length and is resiliently urged against the fine wire windings. The post and the terminal are designed such that the windings on the post are not disturbed when the terminal is crimped thereon and are not contacted other than by the web. An effective electrical connection is achieved not withstanding the frailty of the wire and the wire itself is not damaged. The terminal, on the other hand, is sufficiently massive to permit its being crimped onto a relatively coarse wire which extends from the bobbin.
It is accordingly an object of the invention to provide an electrical connection to an extremely fine wire of the type used for coil windings. A further object is to provide an electrical connection between a relatively coarse wire and an extremely fine wire. A further object is to provide an electrical connection for connecting external wires to the fine wires of a coil winding. A further object is to provide a solderless connection between an extremely fine coil winding and a coarse wire extending from the winding.